Silicon selective epitaxial growth at reduced pressure and temperature

Abstract In a rapid thermal process (RTP) system working at a total pressure of a few Torr, we have obtained selective epitaxial growth (SEG) of silicon at temperatures as low as 650°C. When using SiH 2 Cl 2 (DCS) as the reactive gas no addition of HCI is needed. Nevertheless, using SiH 4 below 950°C a small amount of HCl should be added. The kinetic aspects of the two systems, DCS/HCl/H 2 and SiH 4 /HCl/H 2 , are presented and discussed. For the DCS system we show that the rate-limiting reactions are slightly different from those commonly accepted in the literature, where results are from systems working at atmospheric pressure or in the 20–100 Torr range. The growth rate for our system is found to be a linear function of the partial pressure of hydrogen, as well as the partial pressure of HCl, mainly in the gas phase diffusion-controlled regime. The saturation in growth rate as a function of the DCS input pressure can be explained by our model, as can the non-hydrogen partial pressure dependence in the kinetically-controlled regime. This model is based on the main decomposition of DCS, SiH 2 Cl 2 → SiHCl + HCl, instead of the widely accepted reaction SiH 2 Cl 2 → SiCl 2 + H 2 . This is the main reason why no extra HCl is required in the DCS/H 2 system to obtain full selectivity from above 1000°C down to 650°C.